JP4561522B2 - Sub-chamber internal combustion engine - Google Patents

Description

  The present invention relates to a sub-chamber internal combustion engine in which a combustion chamber includes a main chamber and a sub chamber, and a flame jet is ejected from the sub chamber toward the main chamber to perform combustion in the main chamber.

There exists patent document 1 as a conventional subchamber internal combustion engine. In the invention described in Patent Document 1, a plurality of communication passages communicating the sub chamber (sub combustion chamber) and the main chamber (main combustion chamber) are arranged radially, and a torch-like flame jet generated by combustion in the sub chamber is disposed. These are ejected radially from the nozzle hole of each communication passage toward the main chamber with the cylinder axis as the center. Thereby, stable lean combustion is performed by shortening the flame propagation distance in the main chamber.
JP 2002-81321 PR

However, in patent document 1, there is no clear description about the flame jet ejection angle (the nozzle orientation angle) with respect to the cylinder axis direction for the nozzle holes of each communication passage. For this reason, there is a problem that the flame propagation distance cannot be sufficiently shortened depending on the shape of the combustion chamber.
The present invention has been made in view of the conventional problems as described above, and by reducing the flame propagation distance by optimizing the direction of jetting the flame jet (injection direction) according to the shape of the combustion chamber, the stable dilution An object of the present invention is to provide a structure of a sub-chamber internal combustion engine whose thermal efficiency is improved by combustion.

For this reason, the present invention provides a fuel injection valve that injects fuel from the upper part of the main combustion chamber toward the piston, and a substantially center of the piston crown so as to receive the fuel injected from the fuel injection valve immediately before the compression top dead center. A sub-chamber that is smaller in volume than the main combustion chamber and disposed in the center of the cylinder head, a nozzle that is located at the boundary between the sub-chamber and the main combustion chamber, and that can exchange gas, and a sub-chamber mixture and a spark plug for igniting a, together with the combustion of air-fuel mixture in the main combustion chamber by ejecting torch-like flame into the main combustion chamber from the injection port by ignition in auxiliary combustion chamber, in the low load side stratification In the sub-chamber internal combustion engine that performs combustion and performs homogeneous combustion on the high load side ,
As the nozzle hole, and a first injection port and the second injection port opening at different angles with respect to the cylinder axis their respective one or more,
The first nozzle hole is provided such that its central axis is directed to the inner wall surface of the cylinder bore without colliding with the piston crown surface in the vicinity of the compression top dead center of the piston, and the second nozzle hole has its central axis line However, in the vicinity of the compression top dead center of the piston, it is provided so as to face the outer peripheral portion of the bottom surface of the bowl on the piston crown surface.

With the above configuration, the flame propagation distance can be further shortened by optimizing the directivity directions of the first nozzle hole and the second nozzle hole according to the shape of the combustion chamber. Thereby, lean combustion becomes more stable and the thermal efficiency can be further improved.

Below, 1st Embodiment in this invention is described.
“Up” and “down” mean directions in which the cylinder head side is “up” and the piston side is “down” in the cylinder axis direction.
First, the combustion chamber 22 includes a main chamber 2 (main combustion chamber) and a sub chamber 4 provided above the central portion of the main chamber 2.
As shown in FIG. 1, the main chamber 2 is formed by a cylinder head 24, a cylinder block 26, and a piston 10, and a cross section viewed from above or below is substantially circular, and an intake port 28 and an exhaust port 30. And communicate with each other.
The sub chamber 4 has a smaller volume than the main chamber 2 and has a cylindrical shape extending substantially in the vertical direction at a substantially central portion on the cylinder head 24 side. The sub chamber boundary projects toward the main chamber 2 on a spherical surface of a substantially hemisphere. It is separated from the main room 2 by a wall 6.
The nozzle holes 6 a and 6 b are holes having a circular or elliptical cross-sectional shape, penetrate the sub chamber boundary wall 6, and allow gas exchange between the main chamber 2 and the sub chamber 4.
The intake valve 32 and the exhaust valve 34 open and close the intake port 28 and the exhaust port 30 by driving cams 36 and 38.
The fuel injection valve 40 is disposed in the vicinity of the sub chamber 4 in the upper part of the combustion chamber 22 and directly injects fuel into the cylinder (in the main chamber 2).
The bowl 10b is formed in a substantially circular and concave shape with respect to the vicinity of the center of the crown surface 10a of the piston 10, and the fuel injected from the fuel injection valve 40 substantially downward is immediately before the compression top dead center of the piston 10. Receiving and stratifying the mixture.
The spark plug 12 is disposed in the upper part of the sub chamber 4 and performs spark ignition on the air-fuel mixture in the sub chamber 4.
In the compression stroke having the above configuration, the air-fuel mixture flows from the main chamber 2 toward the sub chamber 4 through the nozzles 6a and 6b. On the other hand, in the combustion expansion stroke, the torch-like flame jets 8a and 8b (see FIG. 2) are respectively supplied from the sub chamber 4 to the main chamber 2 through the nozzle holes 6a and 6b along with the combustion in the sub chamber 4. 6a and 6b are ejected in the directing directions (meaning that the central axes of the nozzle holes 6a and 6b extend toward the main chamber 2), and the air-fuel mixture in the main chamber 2 is combusted.
Next, the nozzle holes 6a and 6b and the flame jets 8a and 8b will be described in detail. In addition, when it describes as "a nozzle group", it points out the aggregate | assembly of a some nozzle hole, and when it writes as "a flame jet group", it points out the aggregate | assembly of a some flame jet.
The directivity directions of the nozzle holes 6a and 6b are different from each other with respect to the cylinder shaft 42. The nozzle holes 6a are directed in the direction of the combustion chamber peripheral wall 18 (cylinder bore) and do not collide with the crown surface 10a. 6b is directed to the vicinity of the bottom surface outer peripheral portion 10c of the bowl 10b (see FIG. 2). For this reason, the flame jet 8a is ejected toward the combustion chamber peripheral wall 18, and the flame jet 8b is ejected toward the bottom surface outer peripheral portion 10c.
As shown in Type 1 of FIG. 3, the nozzle holes 6a and 6b are arranged on the circumference of the circle 14, the nozzle group 6b is on the circumference of the circle 16, and 6 on each circumference. They are arranged at approximately equal intervals. The circle 14 and the circle 16 are respectively formed around the sub chamber central axis (the cylinder central axis of the sub chamber 4), but the circle 14 has a larger diameter than the circle 16, and the nozzle group 6a is formed outside the combustion chamber. A nozzle hole group 6b is disposed inside the combustion chamber (see Type 1 in FIG. 3).
If the nozzle hole groups 6a and 6b are formed on the same circumference, the distance between the nozzle holes becomes small, and the following concerns arise. First, the sub chamber boundary wall 6 has low strength, and when the pressure in the sub chamber 4 increases due to combustion in the sub chamber 4, the sub chamber boundary wall 6 is damaged, or the heat transfer path of the sub chamber boundary wall 6 is narrowed, Prevents heat dissipation. However, the above concerns are eliminated by the configuration of the circles 14 and 16. The difference in the radius values of the circles 14 and 16 and the interval between the nozzle holes on the circumference of the circles 14 and 16 may be set so that adjacent nozzle holes do not approach too much.
The same number (six) of nozzle holes 6a and 6b are arranged in alternating permutation around the sub-chamber central axis (approximately the cylinder axis) (see FIG. 3). That is, when viewed from the direction of the sub chamber central axis (approximately the direction of the cylinder shaft 42), the sub chamber boundary wall center 6c (the sub chamber boundary wall 6 and the sub chamber boundary wall 6 and the sub chamber boundary wall 6) travels around the sub chamber central axis. A straight line extending from the center of the chamber central axis) toward the nozzle hole 6a and a straight line extending from the sub-chamber boundary wall center 6c toward the nozzle hole 6b appear alternately.
When viewed from the orientation direction of the sub-chamber center axis, it is preferable that no other nozzle (no matter whether the nozzle 6a or the nozzle 6b) is arranged on a straight line extending from the sub-chamber boundary wall center 6c toward each nozzle. . At the same time, the directing direction of the nozzle hole 6a coincides with the direction from the sub-chamber boundary wall center 6c toward the nozzle hole 6a, and the directing direction of the nozzle hole 6b matches with the direction from the sub-chamber boundary wall center 6c toward the nozzle hole 6b. Good. Thereby, the flame jet groups 8a and 8b are dispersed and ejected in the main chamber 2 so as not to overlap each other when viewed in the cylinder axial direction (viewed from above or below the combustion chamber). Therefore, the flame jet group 8b supplements flame propagation in a region relatively far from the flame jet group 8a in the main chamber 2, and the flame propagation distance can be shortened almost uniformly over the cylinder axis 42.
Further, in a pent roof type combustion chamber having a squish area or the like, when viewed in the cylinder axial direction, the directing direction of the injection port 6a (the ejection direction of the flame jet group 8a) is the intake-exhaust direction ( It is preferable to incline by a predetermined angle with respect to the direction in which intake or exhaust proceeds from the intake port 28 to the exhaust port 30 (see FIG. 4). Here, the “predetermined angle” is an angle at which the flame jet group 8a can be ejected while avoiding the squish area. The squish area is an area close to the intake port and the exhaust port in the upper part of the combustion chamber 22, and the vertical height is relatively smaller than the other areas in the combustion chamber 22. For this reason, there is a concern that the progress of the flame jet 8a spouted toward the squish area is blocked. Therefore, with the above-described configuration, it is preferable that the flame jet group 8a ejects while avoiding the squish area, the effective reach distance of the flame jet group 8a is increased, and the flame propagation distance is more reliably shortened.
When the distance from the nozzle group 6a to the combustion chamber peripheral wall 18 is larger than the distance from the nozzle group 6b to the crown surface 10a, the smaller the nozzle diameter, the longer the jet length of the flame jet, so the nozzle group 6a. Is smaller than the nozzle hole group 6b, and the length of the flame jet may be adjusted. In the case of a flame jet with an excessive jet length, there is a concern that unburned fuel may remain in the unreached region. On the other hand, with an jet jet with an excessive jet length, this collides with the combustion chamber wall, resulting in an increase in cooling loss. Although there is a concern, the above-mentioned concern can be solved by adjustment in the above configuration.
In addition, the combustion mode of the present embodiment may be stratified combustion as shown in FIG. 5 (A) below a predetermined engine load, and switched to homogeneous combustion as shown in FIG. 5 (B) above a predetermined engine load. . In stratified combustion, an air-fuel mixture is formed in and above the bowl 10b, and the flame jet group 8b is ejected into the air-fuel mixture, enabling rapid and stable combustion even under a lean air-fuel ratio. Here, a part of the fuel is transported in the direction of the peripheral wall of the combustion chamber by the simultaneous jetting of the flame jet group 8a. However, since this fuel is very small and can be burned by the flame jet group 8a, the flame jet group 8a substantially There is no harmful effect.
In the conventional sub-chamber internal combustion engine, the flame limit is greatly increased by the flame jet, and even under high load operation conditions, the combustion is completed before the start of knocking by increasing the combustion speed, thereby improving the torque.
Moreover, in patent document 1, a nozzle hole (communication passage) is formed so that the cross-sectional area may increase toward a main chamber from a sub chamber, and a flame jet is ejected so that it may spread in fan shape in a main chamber, The local uneven distribution of the flame jet is prevented, and the flame propagation distance is shortened.
However, due to the structure of the combustion chamber peripheral wall and the piston crown surface, the injection hole directivity distance from the injection hole to the combustion chamber wall varies depending on the size of the injection hole directivity angle with respect to the cylinder axis, and the single injection nozzle directivity angle is specified. Then, the flame propagation distance cannot be shortened sufficiently.
Further, in lean combustion with a low engine load, formation of a stratified mixture is desirable, and if a pent roof type combustion chamber is formed and a bowl is formed on the piston crown surface, the combustion chamber is not a simple shape. Therefore, in order to shorten the flame propagation distance over the bowl, it is desired to optimize the flame jet direction and its direction with respect to the bowl.
Therefore, when a bowl is formed on the piston crown surface, it is preferable to provide a nozzle that is oriented appropriately for the bowl to enable effective flame propagation to the stratified mixture above the bowl, and to reliably burn it. This makes it possible to shorten the flame propagation distance not only in the circumferential direction of the combustion chamber but also in the entire combustion chamber including the vicinity of the center of the combustion chamber with respect to the directivity angle (flame jet ejection angle) with respect to the cylinder axis. Further, for a complicated combustion chamber structure, an optimal directivity direction may be determined and a nozzle hole may be provided.
Hereinafter, a second embodiment of the present invention will be described.
The difference between this embodiment and 1st Embodiment is having increased the number of nozzle holes (6 pieces) of the nozzle group 6a compared with the number of nozzle holes (4 pieces) of the nozzle group 6b (refer FIG. 6, 7). ). This is because the main chamber 2 has a larger diameter than the bowl 10b, and the flame jet group 8a propagates the flame to a wider area than the flame jet group 8b in order to shorten the flame propagation distance in the entire combustion chamber. This is necessary. In particular, when the amount of fuel entering the sub chamber 4 from the main chamber 2 in the compression stroke (the total momentum of the flame jet) and the ejection length of the flame jets 8a and 8b depend on the cross-sectional area of the nozzles 6a and 6b, the nozzle 6a If the cross-sectional area of 6b is not desired to be changed, the number of nozzles may be adjusted. Further, when the number of nozzle holes (total of the sectional areas of all nozzle holes) is limited, if the nozzle hole 6b has a larger diameter (larger cross-sectional area) than the nozzle hole 6a, the number of nozzle holes 6b is set to be larger than the number of nozzle holes 6a. Reducing it is effective.
Hereinafter, a third embodiment of the present invention will be described.
The difference between the present embodiment and the first embodiment is that the arrangement of the nozzle groups 6a and 6b is exchanged, so that the nozzle group 6b is arranged on the circumference of the circle 14 outside the combustion chamber, and the nozzle group 6a. Is arranged on the circumference of the circle 16 inside the combustion chamber (see Type 2 in FIG. 3).
When the sub-chamber 4 is formed in the cylinder head 24 by casting and then the injection hole 6a substantially parallel to the upper surface of the combustion chamber 22 is processed, there is a concern that the cylinder head 24 and the injection hole 6a approach and the processing becomes difficult. However, in such a case, the change to this embodiment is effective.
Alternatively, in the first embodiment, when the nozzle 6a substantially parallel to the upper surface of the combustion chamber 22 is to be processed more easily, the cylinder head 24 and the sub chamber 4 are manufactured independently, and after processing the nozzles 6a and 6b, the sub chamber 4 may be attached to the cylinder head 24 by screwing or the like.

The present invention is not limited to the above-described embodiment, and may be configured as follows.
First, a fuel injection valve or a gas mixture supply valve for supplying gas or liquid fuel directly in the sub chamber 4 is provided, and a small amount of fuel is injected into the sub chamber 4 so that the sub chamber 4 and the main chamber 2 are injected. It is also possible to adopt a configuration in which the air-fuel mixture formation and the air-fuel mixture concentration are positively different (the sub chamber 4 is richer than the main chamber 2).
Further, the arrangement position of the fuel injection valve 40 is not limited to the upper portion of the combustion chamber, and may be the side portion of the combustion chamber. Alternatively, the fuel injection valve 40 may be arranged in the course of the intake port 28 and homogeneous combustion may be performed regardless of the magnitude of the load.
Further, the number of the nozzle holes 6a and 6b may be at least one each, and even if there are a plurality of nozzle holes 6a and 6b, the number is not limited to the number disclosed in the above embodiment.
Further, a form in which the nozzle holes 6a and 6b are mixed on the circumferences of the circles 14 and 16 is also included in the present invention.

  Further, the number of types of directivity angles of the nozzle holes with respect to the cylinder shaft 42 is not limited to the two types of nozzle holes 6a and 6b, but may be three or more in total. This is particularly preferably set according to the shape of the crown surface 10a (such as the bowl structure).

Front view of the first embodiment of the present invention Explanatory drawing of the combustion chamber shape and nozzle direction in FIG. Structure explanatory drawing of the sub chamber boundary wall of FIG. 1 and the third embodiment of the present invention Schematic diagram of flame jet ejection state in FIG. Explanatory diagram of mixture distribution in stratified charge combustion and homogeneous combustion in FIG. Structure explanatory drawing of the sub chamber boundary wall of 2nd Embodiment in this invention Schematic diagram of flame jet ejection state in FIG.

Explanation of symbols

2 Main room (main combustion chamber)
4 Sub chamber 6 Sub chamber boundary wall (Boundary between sub chamber and main combustion chamber)
6a nozzle (first nozzle)
6b nozzle (second nozzle)
DESCRIPTION OF SYMBOLS 10 Piston 10a Crown surface 10b Bowl 10c Bottom outer peripheral part 12 Spark plug 14 yen 16 yen 18 Combustion chamber peripheral wall (cylinder bore)
22 Combustion chamber 24 Cylinder head 42 Cylinder shaft

Claims (9)

A fuel injection valve for injecting fuel from the upper part of the main combustion chamber toward the piston, and a bowl provided substantially at the center of the piston crown so as to receive the fuel injected from the fuel injection valve immediately before the compression top dead center; Igniting the sub-chamber which is smaller in volume than the main combustion chamber and arranged in the center of the cylinder head side, the nozzle at the boundary between the sub-chamber and the main combustion chamber and capable of gas exchange, and the air-fuel mixture in the sub-chamber An ignition plug, and by igniting in the sub chamber, a torch-like flame is ejected from the nozzle into the main combustion chamber to burn the air-fuel mixture in the main combustion chamber, and stratified combustion is performed on the low load side and high load In the sub-chamber internal combustion engine that performs homogeneous combustion on the side ,
As the nozzle hole, and a first injection port and the second injection port opening at different angles with respect to the cylinder axis their respective one or more,
The first nozzle hole is provided such that its central axis is directed to the inner wall surface of the cylinder bore without colliding with the piston crown surface in the vicinity of the compression top dead center of the piston, and the second nozzle hole has its central axis line However, in the vicinity of the compression top dead center of the piston , the sub-chamber internal combustion engine is provided so as to face the outer peripheral portion of the bottom surface of the bowl on the piston crown surface . Wherein the diameter of the first injection port, the sub-chamber type internal combustion engine according to claim 1, characterized in that the smaller than the diameter of the second injection port. 3. The sub-chamber internal combustion engine according to claim 1, wherein the first nozzle hole and the second nozzle hole have respective center positions that are substantially coincident with each other and open on circumferences having different radii. . 4. The sub-chamber internal combustion engine according to claim 3 , wherein the first nozzle hole is opened on an outer circumference with respect to the second nozzle hole. 5. 4. The sub-chamber internal combustion engine according to claim 3 , wherein the first nozzle hole opens on an inner circumference with respect to the second nozzle hole. 5. The said 1st nozzle hole and said 2nd nozzle hole are each opened in the permutation which is a circumference direction around a cylinder axis | shaft alternately, The one of Claims 1-5 characterized by the above-mentioned. Sub-chamber internal combustion engine. Wherein the number of first injection port, the sub-chamber type internal combustion engine as set forth in any one of claims 1 to 5, characterized in that more than the number of the second injection port. A pent roof type combustion chamber having a squish area is provided, and the first nozzle hole has a predetermined angle with respect to a straight line connecting the intake and exhaust directions when the central axis is viewed in the cylinder axial direction. The sub-chamber internal combustion engine according to any one of claims 1 to 7 , wherein the sub-chamber internal combustion engine is provided. When viewed in the cylinder axis direction,
The first nozzle hole and the second nozzle hole are disposed away from a straight line extending from the sub-chamber boundary wall center toward another nozzle hole,
The directivity direction of the first nozzle hole substantially coincides with the direction from the center of the sub-chamber boundary wall toward the first nozzle hole,
The sub-direction according to any one of claims 1 to 8 , wherein a directivity direction of the second nozzle hole substantially coincides with a direction from the center of the sub-chamber boundary wall toward the second nozzle hole. Chamber internal combustion engine.